As Shropshirerosie says sometimes you have to make the rules as you go.
Another thing you could try is just not making her go. Sit her out. Ask her to move and then when she will not just sit on her. Sit heavy with your weight towards the back of the saddle making it uncomfortable for her. Do nothing, eat your sandwiches, have a drink, picnic on horseback, she will want to move at one point or another and it might be a long time but when she wants to move, you make her wait for another minute and then ask her to go on your terms.
It can take over an hour (most for me was three hours) but each time it gets less and less.